Modern attempts at Diptera family classification are based on the work of Willi Hennig (1948, 1952, 1954, 1958, 1965, 1971), which was summarized in this treatment in the Handbook of Zoology in 1973. This was the last united version of Diptera family classification. Since then numerous papers on various groups have been published.

The following list follows the hierarchy of the Manual of Nearctic Diptera Vol. 3 (Wood & Borkent, 1989, Woodley, 1989, J. F. McAlpine 1989) and families of Hennig (1973). Within each higher group the families are ordered alphabetically. For each change from there in the higher classification we have written a note as to why, usually providing a citation.

Decisions about the status of several taxa are difficult because they are either a question of rank (e.g. Mythicomyiidae) or because they are about non-monophyletic units (e.g. Empididae, Calliphoridae) where current information is limited. One way to decide about the question of rank is to follow Hennig (1950, 1966) in determining the rank based on the age of the group. However, this approach is not accepted generally. Therefore we rather follow consensus between the participating dipterists in our classification and have largely accepted a “splitter” classification as our classification represents a pragmatic starting point for future research. The question of non-monophyletic groups will resolve itself as knowledge becomes better. For the time being we will pragmatically keep some of these groups as traditionally defined until we know more.

In the family classification we have added "(rank)" to all taxa which hold a basal position within the respective family and are therefore subject to discussions about the rank of the taxon (see above). All other subordinate taxa are treated as "(synonym)."

A list of major references of Diptera family classification (1950-2003) (but see also those included in Yeates & Wiegmann 1999) are included in our Source document and also are in the Reference database.

Tipulidae/Cylindrotomidae/Limoniidae/Pediciidae: The current European view is four separate families: Cylindrotomidae, Pediciidae and Tipulidae are clearly monophyletic units, Limoniidae paraphyletic (Oosterbroek 1986, Oosterbroek & Theowald 1991, Stary 1992). American view (Alexander and others (Wood & Borkent 1989)) is one very ancient diversified clade that needs its phylogenetic relationship to be completely resolved before any subordinate clades can be recognized or not. The European view is accepted here.

We follow Amorim (2000) in recognizing one family Canthyloscelidae (Hyperoscelididae of Hennig 1973), which includes Synneuridae.

The Psychodidae are paraphyletic and perhaps polyphyletic. However, following Hennig (1972), we accepted them as monophyletic.

Phlebotomidae are treated as a subfamily of Psychodidae in Hennig (1973)

Leptoconopidae are a subfamily of Ceratopogonidae according to Hennig (1973). Some authors (Remm 1988 and the Zoological Record) have recognized this basal clade at the family level.

We follow Wood & Borkent (1989) in recognizing Corethrellidae (formerly in Chaoboridae) as a valid family.

Olbiogastridae and Mycetobiidae are treated as subordinate taxa of Anisopodidae following Hennig (1973). Amorim and Tozon (1994) treated them as valid families.

Penthetriidae and Pleciidae are basal taxa within Bibionidae following Pinto & Amorim (2000).

Baeonotidae and Lestremiidae are subordinate groups within Cecidomyiidae according to Gagne (1981).

Macroceridae are a subordinate group of Keroplatidae in Hennig (1973) as well as Matile (1990, 1997)

We follow Thompson (1975, Grimaldi & Blagoderov 2001) in recognizing the Lygistorrhinidae as a valid family.

We follow Wood & Borkent (1989) in recognizing Cramptonomyiidae as a subfamily of Pachyneuridae.

The Manotidae are a subordinate rank of Mycetophilidae according to Matile (1990, 1997) and Soli (2002).

We follow Chandler's phylogenetic tree (2002) in placing the Heterotrichia group within Sciaridae and the genus Pterogymnus Freeman is placed in the Sciaridae.

The infraorder Axymyiomorpha was proposed for the single family Axymyidae by Wood & Borkent (1989).

The family Oreoleptidae was described by Zloty, Sinclair & Pritchard (2005) for the genus Oreoleptis. According to their phylogenetic analysis Oreoleptis is the sister taxon of Athericidae+Tabanidae and cannot thus be included in Rhagionidae.

We follow Woodley (1989) in recognizing the Coenomyiidae and Rachiceridae as subordinate groups of Xylophagidae. The Exeretonevridae and Heterostomidae were placed as taxa incertae sedis within the Xylophagomorpha by Woodley, but we follow Palmer & Yeates (2000) in recognizing them as subordinate groups of Xylophagidae.

The family Athericidae was erected by Stuckenberg (1973) for several genera previously associated with Rhagionidae.

The Pelecorhynchidae are a subordinate rank of Rhagionidae according to Stuckenberg (2001).

Following Stuckenberg (2001), Spaniidae and Austroleptidae are recognized at family rank.

Vermileonidae were given family rank by Nagatomi (1977) and accepted by Woodley (1989).

Apsilocephalidae were given family status by Nagatomi et al. (1991) and accepted by Yeates et al. (2003).

The Apystomyiidae were given family status incertae sedis in Asiloidea by Nagatomi & Liu (1994).

We follow Woodley (1989) and Yeates (2001) in recognizing Hilarimorphidae as a valid family.

The Mythicomyiidae are the sister group of Bombyliidae (Yeates 1994). Following Hennig's age criterion they are treated at family rank (Zaitzev 1991, Evenhuis 1994) in our classification.

The new family Ocoidae was described by Yeates et al. (2003).

The Empididae sensu Hennig (1973) were divided into four families: Empididae, Atelestidae, Hybotidae, and Microphoridae by Chvala (1983) and Collins & Wiegmann (2002). However, according to Collins & Wiegmann's phylogenetic analysis the Empididae (s. s.) are still paraphyletic with regard to the Hybotidae. Also, Microphoridae may be paraphyletic in respect to Dolichopodidae. Hence until there is better resolution, we continue to follow Hennig (1973).

We follow Chandler (1991) and Cumming et al. (1995) in recognizing Opetiidae at family rank (see also, Disney 1987, Chandler 2001).

Termitoxeniidae are a subordinate group of Phoridae according to Hennig (1973). Sciadoceridae are a subordinate group of Phoridae according to Disney (2001).

Microdontidae are a subordinate group of Syrphidae according to Hennig (1973). Thompson (1969, also 1972) showed its basal position in respect to other syrphids and this position is supported by molecular evidence (Stahls et alia 2003)

The Calliphoridae are marked as a polyphyletic group of convenience as at the present we are unwilling to reduce the Oestridae to a subordinated group within a monophyletic Calliphoridae nor to elevate a number of other groups (Polleniidae, Helicoboscidae, and Bengaliidae) so as to properly delimit both Calliphoridae and Oestridae. This follows from the analysis of Rognes (1997). Also, given the relative precedence of the family group names, a broad all inclusive group would have to be called Oestridae which would cause much confusion among general users given the importances of both the bots and blow flies.

We follow Griffiths (1972) in placing the Nycteribiidae and Streblidae as subordinate groups of Hippoboscidae.

We follow J. F. McAlpine (1989) in placing the Eginiidae as a subordinate group of Muscidae.

The Mystacinobiidae are the sister group of all other Oestroidea according to Rognes (1997) and are here recognized as separate family.

Cuterebridae, Gasterophilidae, and Hypodermatidae were given subfamily rank within Oestridae by Wood (1987) and Pape (2001).

Rhiniidae are given family rank due to their basal position among the "calliphorids" following the analysis of Rognes (1997).

Axiniidae> are considered to belong within the Rhinophoridae following Pape (2001).

Stackelbergomyiidae belong to the Tachinidae according to Herting (1981).

The Pseudopomyzidae are treated as subfamily of Cypselosomatidae following J. F. McAlpine (1989). However, they were retained as a separate family by D. K. McAlpine (1996).

Calobatidae, Taeniapteridae, and Tylidae are treated as subordinate groups of Micropezidae following D. K. McAlpine (1998).

Gobryidae were described by D. K. McAlpine (1997).

The Somatiidae were established as a family by Hendel (1935), but were treated by Hennig (1973) as a possible genus of Psilidae. They were removed by D. K. McAlpine (1997) from Diopsoidea to incertae sedis. However, for pragmatic reasons we keep them in the Diopsoidea until further research reveals a better placement.

The Tanypezidae were removed by D. K. McAlpine (1997) from Diopsoidea to incertae sedis. However, for pragmatic reasons we keep them in the Diopsoidea until further research reveals a better placement.

Stylogasteridae are a subfamily of Conopidae following Hennig (1973).

Eurygnathomyiidae are a subordinate rank of Pallopteridae following Hennig (1973).

Neottiophilidae and Thyreophoridae were treated as subordinate groups of Piophilidae by J. F. McAlpine (1977).

The Tachiniscidae were placed as the basal sister to the other fruit flies in an enlarged definition of Tephritidae by Korneyev (1999).

Phytalmiidae are a subordinate group of Tephritidae according to Hennig (1973).

Ulidiidae/Otitidae: Kameneva & Korneyev (1994) pointed out the priority of Ulidiidae and used it as the name for a single family consisting of the two subfamilies Ulidiinae and Otitinae. However, in his catalog of family-group names Sabrosky (1999) kept Otitidae as the valid family name following the use in all modern regional catalogs except for the Palearctic catalog. We follow Kameneva & Korneyev in recognizing a single family Ulidiidae. Euxestidae is a subordinate group of Ulidiinae and Pterocallidae is a subordinate group of Otitinae according to Hennig (1973).

We follow D. K. McAlpine (1990) in recognizing Ctenostylidae as a valid family.

Cremifaniidae were treated as subfamily of Chamaemyiidae by Hennig (1973).

Phycodromidae is an old synonymous name for Coelopidae (Sabrosky 1999).

Helcomyzidae and Heterocheilidae are recognized as valid families following McAlpine (1991c, 1991b).

We follow Griffiths (1972) and Barnes (1981) in recognizing Helosciomyzidae as a valid family.

Huttoninidae are recognized as a valid family following D. K. McAlpine (1991b, also Colless & McAlpine 1991).

Phaeomyiidae are recognized as a valid family following Griffiths (1972).

Marginidae were described by D. K. McAlpine (1991) and provisionally admitted to the Opomyzoidea.

We recognize Neminidae as a valid family following Freidberg (1994).

Neurochaetidae were described by D. K. McAlpine (1978).

Stenomicra was placed in Aulacigastridae by Hennig (1973), but was raised to family level by Papp (1984). However, we follow D. K. McAlpine (1978, 1983) and Mathis & Papp (1992) in treating Stenomicridae as a subordinate group of Periscelididae.

Xenasteiidae were described by Hardy (1980), followed four months later by a description of Tunisimyiidae by Papp (1980). Tunisimyiidae was synonomized with Xenasteiidae by J. F. McAlpine (1989).

The Acartophthalmidae belong to the superfamily Carnoidea according to Brake (2000) and Buck (2006).

Australimyzidae were raised to family level by Griffiths (1972) and confirmed as a separate family from Carnidae by Buck (2006).

Tethinidae are paraphyletic with respect to Canacidae. Canacidae is the older name and therefore has priority (Buck 2006, D. K. McAlpine 2007).

We follow Andersson (1977) and J. F. McAlpine (1989) in treating the Siphonellopsidae (raised to family level by Nartshuk in 1983) as a subfamily of Chloropidae.

Inbiomyiidae were described by Buck (2006)

We follow D. K. McAlpine (1985) in including Borboropsidae, Chiropteromyidae, Cnemospathidae, Heteromyzidae, Notomyzidae, Rhinotoridae, and Trixoscelididae in the family Heleomyzidae.

Nannodastiidae were established as a separate family by Carles-Tolra (1994), but whether this group really constitutes a valid family remains doubtful (Papp & Mathis, 2001).

Campichoetidae were raised to family status by Griffiths 1972 (also Chandler 1987), however this view was rejected by J. F. McAlpine (1987). We follow the latter in keeping the Campichoetidae as a subordinate group of Diastatidae.

Risidae are a subordinate group of Ephydridae according to Freidberg et al. (1998).